<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
      .bg{
        color:black;
        width: 150px;
        height: 150px;
      }
      .bg:hover{
        color:blue
      }
    </style>
</head>
<body>
  <div class="bg" href="">我应该会变色</div>
</body>
</html>